An ignition system that is based on the alternating (AC) rather than the traditional direct (DC) current in the spark plug discharge has been developed at the Caterpillar Technical Center. This system can generate a long duration discharge with controllable power. It is believed that such an ignition system can provide both a leaner operating limit and a longer spark plug life than a traditional DC system due to the long discharge duration and the low discharge power. The AC ignition system has successfully been tested on a Caterpillar single cylinder G3500 natural gas engine to determine the effects on the engine performance, combustion characteristics and emissions. The test results indicate that while the AC ignition system has only a small impact on engine performance (with respect to a traditional DC system), it does extend the lean limit with lower NOx emissions. Evidences also show the potential of reduce spark plug electrode erosions from the low breakdown and sustaining discharge powers from the AC ignition system. This paper summarizes the prototype design and engine demonstration results of the AC ignition system.

This content is only available via PDF.
You do not currently have access to this content.